In recent years LCD technology has been well developed, the cost of LCD drops significantly. As a result, it gradually replaces the traditional CRT in the home appliances. The competition in the market place is fierce. To provide distinguished product features is a high priority R & D issue in the LCD market. For instance, R.O.C. patent publication No. 200534569 discloses two types of driving circuits. The first type of driving circuit provides an AC signal from a power source to a power supply, then the power supply transforms voltage to output an electric signal to an inverter to boost the voltage and output a high voltage electric signal. The present power supply to process the AC signal output from the power source includes an electromagnetic interference (EMI) filter unit, a commutation unit, a power factor corrector and a conversion unit. The EMI filter unit and commutation unit receive the AC signal to perform filtering and commutation processes and output a full wave/half wave DC signal, then the power factor corrector receives the full wave/half wave DC signal and performs power factor correction to output an electric signal to the conversion unit (DC-DC) which transforms voltage to output a low voltage signal to the inverter. The inverter boosts the voltage to become a high voltage electric signal to be sent to a load linking to a rear end.
Another type of driving circuit differs from the previous circuit as follow: the AC signal output from the power source is received by the EMI filter unit and commutation unit for filtering and commutation processes, and becomes a full wave/half wave DC signal to be output. The full wave/half wave DC signal is an intermediate voltage electric signal (such as the power source being 100V, the full wave/half wave DC signal being 150V). The intermediate voltage electric signal is sent to an inverter for voltage boosting to become a high voltage electric signal to be output to a load.
When the conventional driving circuits mentioned above are adopted on a flat panel display device, only the high voltage electric signal is provided to the load (namely a cold cathode fluorescent lamp CCFL). As a result, no extra connection ports are added to the present display devices on the market. Users have to couple required peripheral devices by themselves, such as speakers, small lamps, ear sets, USB connection ports, or small 3C products sensible to screen images to generate interactions. Another approach is to provide a low voltage power cord and a mating low voltage driving circuit to support the LCD screen of the peripheral devices. All the aforesaid approaches result in a higher cost and a longer production process. They create a greater burden to manufacturers and consumers.
A power supply capable of providing high voltage output power and low voltage power to be used on display devices not only can reduce the cost and production process, also increase utilization efficiency and flexibility, and enhance competitiveness on the market.